1. Technical Field
The present invention is intended to provide an image processing apparatus, an image forming apparatus, an image processing method, a computer program and a recording medium, in which a pattern associated with a chromatic watermark or an achromatic watermark for copy control, which appears as a result of making a copy, is allowed to be generated depending on each color in the case of generating watermark data associated with the watermark.
2. Description of Related Art
Certified copies (e.g., family registers and certificates of residence) published by official agencies on the basis of original documents containing personal information are widely used as papers for authenticating individuals. In order to ensure the function as papers for authenticating individuals, certified copies are required to be distinguished clearly from duplications thereof. Moreover, certified copies published by official agencies require measures to protect privacy, since personal information is contained therein.
Documents printed on the basis of original documents in companies also require measures to protect privacy as well as the certified copies described above, since personal information such as customer information is sometimes contained therein. Moreover, when commercial or technical confidential information is contained in documents created in companies, it is necessary to prevent leakage of the documents to a third party who is under no obligation to keep secrets.
Japanese Patent Application Laid-Open No. 2007-88763 discloses a print control unit for causing a computer to join contents data (original image data) indicative of information contained in an original document with watermark data indicative of a watermark for copy control (e.g., a text or a mark for warning such as “COPY”, “COPY PROHIBITED” or “CONFIDENTIAL”), which is invisible in a certified copy or a document but appears in the duplication of a certified copy or a document made by a copying machine, and printing a certified copy or a document on the basis of obtained composite data. The print control unit can cause a computer to join original image data with watermark data and print an image associated with the watermark data and the original image data on normal paper, eliminating the need to use anti-copying and anti-counterfeiting paper having a watermark printed thereon in advance. Moreover, the user is allowed to select easily a watermark appropriate for the information contained in a certified copy or a document.
In recent years, an image forming apparatus for causing an image reading unit to read an original document printed on paper to generate original image data and joining the generated original image data with watermark data to form an image showing a certified copy or a document has also been proposed in view of a case where the original document is not digitized. An image forming apparatus enables formation of a chromatic (color) image showing a certified copy or a document and advance specification of a chromatic color to be used for a watermark for copy control.